The overall objective of this proposal is to develop new immunologic probes for studying the intracellular dynamics of progesterone receptors. Our specific aims for this period of study are to: 1. Purify different forms of uterine progesterone receptor (Rp) by double DNA-cellulose chromatography and steroid-affinity chromatography procedures. Corticosteroid-binding globulin (CBG) will be used as a stable reference protein. 2. Develop conventional and monoclonal antibodies to different forms of Rp and to different domains of the Rp molecule. 3. Utilize Rp antibodies for new studies of : a) Rp localization in normal and cancer cells b) Rp synthesis and degradation- effects of estrogen and progesterone c) Rp purification by specific antibody columns d) Rp processing in the nucleus e) Rp binding to nuclear acceptor sites.